#include <stdio.h>

void print_demo_first() {
    printf("demo first\n");
}

void print_demo_second() {
    printf("demo second \n");
}

void print_demo_third() {
    printf("demo third \n");
}
// 若是存在if else 语句可能会出错
// #define TEST() print_demo_first();print_demo_second();
#define TEST() do { \
    print_demo_first(); \
    print_demo_second(); \
} while(0)

int main () {
    int n = 0;
    printf(" please input a data:");
    scanf("%d", &n);
    if (n % 2 == 0) 
        TEST();
    else 
        print_demo_third();
        
    return 0;
}